As the packaging containers, there have recently been used various kinds of plastic containers because of their various advantages such as the light-weight properties, the high transparency and the easy moldability of the plastic material.
The plastic container is inferior in the oxygen-barrier properties as compared with the metallic container and the glass container and for this reason, a problem arises such that the contents packed in the plastic containers may undergo a change in quality and cause the reduction of the aromatic properties.
The plastic container is so designed that the wall of the container has a multi-layer structure which includes at least one layer composed of a resin excellent in the oxygen-barrier properties such as an ethylene-vinyl alcohol copolymer to solve the foregoing problem. Alternatively, there has also been known a container which is so designed that it comprises an oxygen-absorptive layer to remove oxygen which may remain in the container and/or the external oxygen which may transmit through the wall of the container. As oxygen absorptive agents (deoxidizing agents) used in the oxygen absorptive layer, there may be listed, for instance, those each mainly comprising a reducing substance such as iron powder (such as those disclosed in Patent Document 1 specified below); and those which make use of an oxygen-scavenger consisting of an ethylenically unsaturated hydrocarbon and a transition metal catalyst (such as those disclosed in Patent Documents 2 to 4 specified below).
However, such a method that an oxygen absorptive agent such as iron powder is incorporated into a resin and the resulting mixture is used for forming the wall of a packaging material is satisfied in that it has a high ability of absorbing oxygen, but this method has a restriction in the applications thereof such that it cannot be applied to the field of packaging materials which should satisfy the requirement of transparency for the purpose of coloring the resin with a particular tint or hue. Moreover, in the method which makes use of an oxygen scavenger consisting of an ethylenically unsaturated hydrocarbon and a transition metal catalyst, the ethylenically unsaturated hydrocarbon absorbs, by itself, oxygen to thus achieve the desired oxygen-barrier characteristics and therefore, it is necessary to increase, to some extent, the amount thereof to be incorporated into the resin, but a problem arises such that if the amount thereof to be added is too great, the moldability and transparency of the resulting resin material is inversely reduced. In addition, in case of these materials using a transition metal catalyst, another problem arises such that after the materials are formed into sheets and bottles, it takes a long period of time (induction time) till these articles initiate the absorption of oxygen.
Thus, there has been proposed a technique for shortening the induction time. For instance, Patent Document 5 discloses that the induction time of the oxygen absorption can be shortened by kneading a resin composition, which comprises a saturated thermoplastic resin such as hydrogenated styrene-butadiene resin and a transition metal catalyst, in the presence of oxygen. This technique uses, as such a catalyst, synthetic calcium silicate impregnated with a transition metal (or a transition metal supported on synthetic calcium silicate). If using such a catalyst supported on a carrier, however, a large amount of such a catalyst should be used to ensure a desired oxygen absorptive properties and this would adversely affects the characteristic properties of the resulting oxygen absorptive resin article. On the other hand, Patent Document 6 discloses that the oxygen-barrier characteristics can be improved when subjecting, to a heat treatment, a sheet or a container consisting of a resin composition which comprises a polyolefin, an oxidation catalyst and a radical-inhibitor in an amount ranging from 0 to 500 ppm.    Patent Document 1: J.P. KOKOKU Sho 62-1824;    Patent Document 2: JP-A-2001-39475;    Patent Document 3: JP-A-5-115776;    Patent Document 4: TOKUHYO Hei 8-502306;    Patent Document 5: JP-A-2004-269735;    Patent Document 6: JP-A-5-51049.